Abstract: Objective To extract and purify the active component from Solanum xanthocarpum for Oncomelania snail control, evaluate its effect against the snails and determine its chemical structure. Methods Pedicel and seed were moved and the remaining part of the Solanum xanthocarpum fruit was torrefied and ground into powder. The powder was soaked into 95% ethanol and extracted. The residue was treated by ethyl acetate. 7 components were separated by methods of thin layer chromatography (TLC) and column chromatography (CCL). 4 main components were observed for the effect of snail-killing by immersion method. An alkaloid with Rf=0.58, named as component A, was confirmed as one of the effective components for Oncomelania snail control. The component A was further purified and received A1 and A2 by proper elusion, and their effect was re-tested. The molecular weight and chemical structure of A2 were determined by MS, NMR and IR respectively. Results The death rate of Oncomelania snails was 94.2% when the concentration of component A was 2.50 mg/L(28 ℃). The flow liquid system (ethyl acetate: chloroform: methanol=11∶11∶35) applied was the best reagent for separating component A. The death rate of Oncomelania snails in solution of A2 (0.2 mg/L) was 100%(28 ℃).The molecular weight of A2 was 867 with an mp 298-305 ℃. Conclusion The effective agent (A2),one of the active components from the fruit of Solanum xanthocarpum, is α-solamarrgine which shows an excellent effect in killing Oncomela snails.

Key words: Solanum xanthocarpum, Molluscacides, Oncomelania hupensis